[rescue] reading old unix disks from Linux

Doug McIntyre merlyn at geeks.org
Fri Apr 26 11:11:33 CDT 2019

On Fri, Apr 26, 2019 at 05:46:57AM -0400, Andrew K. Bressen wrote:
> I have old SCSI drives I'm trying to read, and I'm running into a number
> of different issues I'd welcome feedback on.
> I've got drives from PCs, Macs, Suns, and DEC machines, and I'm using a
> 32 bit linux box (3.x kernel) to read them all. One thing I'm 
> wondering is if I'd have fewer problems booting off a FreeBSD or NetBSD
> liveCD. 

Honestly, I'd try to get images of those drives read into some virtual
format, and run emulators of each of the systems you are trying to
read from. Even a PC version of Solaris would probably do much better
reading a SPARC solaris disk than any other OS. 

UFS is not implemented the same. Disk partitioning never was the same.
Sun did way different than DEC, which was different than AIX, which
was different than HPUX, even if they all used UFS. None of them
partitioned the basic disks the same. 

> In a few cases, I've mounted partitions and seen only a lost+found
> directory that's empty. And dated sometime in the 1990s. But if I 
> run strings(1) on the dd files of the raw partitions, I see tons
> of stuff there. So, am I seeing the remains of deleted files, or
> is the UFS driver buggy or having a poor interaction with the kernel's
> determination of partitions? Is there an undelete tool for antique UFS?

I'd think that if you did get it to mount to a point where you could
see /lost+found that you found a combination of the proper settings to
really read the disk, and most likely the files were "erased", which just
means that the directory node entry was removed, and the datablocks
put in the available pool (just like any OS does), while leaving
the contents of the file still in all its old disk blocks for you to read.

BSD systems come with 'fsdb' to repair UFS file systems, but it requires
a knowledge of the way UFS works, and lots of manual fiddling.
I don't know of any general purpose undelete tools, although I'm sure
people have proprietary inhouse solutions somewhere (ie. FBI/NSA/Ontrack)

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